Trash can- acquire a metal trash can and hack-saw off the bottom. Cover the rough edge in padded tape or duct tape to prevent cutting yourself later. Attach shoulder straps by drilling holes into the can (two in the front and two in the back) and tying the straps through the holes. I made my shoulder straps pretty long so the can was around my waist when I walked (I'm holding it up in the pictures). If you're over 21 feel free to cut the top off of a large plastic bottle and duct tape it securely into the can. This will serve as your drink holder for the night!
Hat- acquire a flat cap, soft green material, brown fur strip, one styrofoam ball (cut in half to make two eyes), and two black buttons. Cover the hat in the green fur. Attach the two styrofoam ball halves to the fur using super glue (or carefully sewing them on) to make the eyes. Glue the black buttons onto the styrofoam to make the pupils of the eyes, feel free to make these a bit "googly". Attach the strip of brown fur over the eyes to make an angry looking uni-brow.
Outfit- anything green is perfect as the trash can will cover most of it.